There is a known microscope in which light is caused to enter a specimen along a direction intersecting the detection light axis of a detection optical system, and a three-dimensional stereoscopic image of the specimen is acquired on the basis of fluorescence that comes from the specimen and that is detected by the detection optical system (refer to, for example, Patent Literature 1 and Patent Literature 2 below). Because no regions other than the image acquisition plane are irradiated with light in these microscopes described in Patent Literature 1 and Patent Literature 2, it is possible to acquire a superior three-dimensional stereoscopic image by suppressing fluorescence fading.
Today, this technique is gaining attention not only as a technique for the purpose of obtaining a stereoscopic image of a living organism, such as zebrafish, in which target molecules are labeled with fluorescent proteins, but also as a technique that is applied to so-called drug development screening, in which pharmaceutical efficacy is evaluated by using an image analysis technique by obtaining a three-dimensional stereoscopic image of three-dimensional cultured cells, such as spheroids or organoids (artificial organ or a portion thereof), thus raising expectations for use in a wide range of applications. In addition, with this observation method there is a demand for more microscopic, higher-resolution observation in response to the desire of researchers to perform observation at resolutions with which individual cells are recognizable.
An immersion objective lens is used with this observation method in the microscopes described in Patent Literatures 1 and 2. With the microscope described in Patent Literature 1, however, when an observation position is changed by moving the container relative to the objective lens, the amount of the liquid immersion medium reserved between the objective lens and the container is reduced, and hence the liquid immersion medium needs to be replenished. In particular, this causes an inconvenience in that the longer the relative moving distance between the objective lens and the container, such as in cases where the container is composed of a plurality of arrays, the more frequently the liquid immersion medium needs to be replenished, requiring a large amount of liquid immersion medium to be prepared. There is another inconvenience in that because replenishment takes a long time, the total observation time becomes longer as replenishment becomes more frequent.
On the other hand, in the microscope described in Patent Literature 2, a sample is accommodated in a cuvette filled with a liquid immersion medium, such as a transparent solution, and, this cuvette is further accommodated in a chamber filled with liquid immersion medium and placed on an XYZ stage. In addition, the leading end section of the objective lens used for observation is immersed in the liquid immersion medium in the chamber via an anti-leak sealing member. According to the structure of the microscope in Patent Literature 2, the amount of liquid immersion medium is not reduced even when the XYZ stage is moved, and hence the above-described inconvenience with the microscope described in Patent Literature 1 can be solved.